Recent trends in integrated circuits is the inclusion of all analog functional blocks in a single chip. In doing so, however, consideration has to be given to the fact that there are different voltage requirements for different functional blocks on a chip. For instance, the power supply voltage will typically be quite different from the signal voltage of the input and output signals. The analog blocks may therefore be required to provide the necessary power supply for certain output devices such as USB devices. This is seen, for example, in the automotive industry where new standards require a supply voltage level of 42 V. Thus integrated circuits, which now abound in motor vehicles, have to be compatible with the particular power supply level. The need for a cost-effective solution becomes particularly significant in the case of low cost electronics such as imaging and low cost sensors. Using high voltage processes for such applications is therefore economically not feasible. An alternative approach is to use a multiple chip solution to perform the voltage conversion. However, this is not only cumbersome but also costly.
A cost effective solution to handling different voltage levels is therefore required. For example, National Semiconductor Corporation deals with bi-directional ESD protection devices implemented in a 5 V process that have to provide 60V ESD protection at the input pads while the core of the chip still uses 5V.
More generally, it is desirable to be able to provide a semiconductor chip with different functional blocks operating at different voltage levels or having different breakdown voltages. Furthermore it is desirable to achieve this without having to incur additional process steps, such as additional mask or doping steps.